Ecografía diafragmática perioperatoria en el punto de atención como herramienta de predicción de fallo respiratorio postoperatorio en pacientes de alto riesgo: estudio de viabilidad y serie de casos / Perioperative diaphragm point-of-care ultrasound as a prediction tool of postoperative respiratory failure in high-risk patients: A feasibility study and case series

Introducción: La función muscular respiratoria en el período postoperatorio es clave para determinar si un paciente desarrollará insuficiencia respiratoria postoperatoria (IRP) o no. La IRP ocurre cuando el intercambio de gases no satisface las necesidades metabólicas. La parálisis ipsilateral del hemidiafragma después del bloqueo del plexo braquial interescalénico (BPBI) provoca una reducción aguda de la función muscular respiratoria. Esta reducción no causa IRP cuando el hemidiafragma contralateral genera suficiente intercambio de gases para satisfacer las demandas metabólicas. Objetivos: Estudiar la evolución de la función muscular hemidiafragmática durante el perioperatorio mediante ecografía diafragmática (D-POCUS) y usarlo como una herramienta innovadora de predicción de IRP valorando el hemidiafragma contralateral en caso de que ocurra una parálisis hemidiafragmática aguda. Métodos: Se estudian pacientes considerados de alto riesgo programados para cirugía de hombro con BPBI. Se evalúan ecográficamente ambos hemidiafragmas, antes y después del procedimiento, mediante fracción de acortamiento (FA) y excursión diafragmática (ED). Se registró en URPA los pacientes con IRP. Resultados: En los 6 pacientes estudiados se produjo una reducción significativa de la FA y la ED del hemidiafragma ipsilateral. Solo 1/6 mostró signos de IRP. La evaluación del hemidiafragma contralateral durante el postoperatorio mostró que en los 5 pacientes sin signos de IRP no existieron cambios significativos en la función del hemidiafragma contralateral. El único paciente que mostró una caída de la función hemidiafragmática contralateral fue el único paciente que padeció IRP. Conclusiones: En esta serie de casos D-POCUS permite conocer la función perioperatoria del diafragma en pacientes de alto riesgo. Todos los pacientes sufrieron una reducción de la FA y la excursión hemidiafragmática aguda tras BPBI; sin embargo, estos pacientes no desarrollaron...(AU)

Introduction: Respiratory muscle function in the postoperative period is a key to whether a patient develops Postoperative Respiratory Failure (PRF) or not. PRF occurs when the gas exchange does not meet metabolic needs. Ipsilateral paralysis of the hemidiaphragm after interscalenic brachial plexus block (ISB) causes an acute reduction of respiratory muscle function. This reduction does not cause PRF when the contralateral hemidiaphragm generates enough gas exchange to meet metabolic demands. Objectives: To study the evolution of hemidiaphragmatic muscle function during the perioperative period with diaphragmatic ultrasound (D-POCUS), and use it as an innovative tool to predict PRF, assessing the contralateral hemidiaphragm in the event of acute hemidiaphragm paralysis. Methods: Patients considered high risk, scheduled for shoulder surgery with ISB are studied. Both hemidiaphragms were evaluated by ultrasound, before and after the procedure, measuring Thickening Fraction (TF) and Diaphragmatic Excursion (DE). PACU patients with PRF were registered. Results: There was a significant reduction in the TF and DE of the ipsilateral hemidiaphragm in the six patients studied. Only 1/6 patients showed signs of PRF. The evaluation of the contralateral hemidiaphragm during the postoperative period showed that in the five patients without signs of PRF, there were no significant changes in the function of the contralateral hemidiaphragm. The patient, who showed a reduction in contralateral hemidiaphragm function, was the only one who suffered PRF. Conclusions: In this case series, D-POCUS allows to know the perioperative function of the diaphragm in high-risk patients. All patients suffered an acute reduction of hemidiaphragm function after ISB; however, these patients did not develop PRF when the contralateral hemidiaphragm function was preserved.(AU)

Continuous-flow electrocoagulation (EC) process for iron removal from water: Experimental, statistical and economic study.

The process of Electrocoagulation (EC), the in-situ production of coagulants by passing an electric current through sacrificial electrodes, is free of chemical additives and cost-effective. This makes it the most widely used water and wastewater treatment method. However, the literature highlights some significant drawbacks of this method including EC unit design limitations. This research therefore aimed to develop a new EC unit design using drilled plates (electrodes) to mix the solution being treated without using external mixers, this minimising power consumption. The performance of the new EC unit was validated by applying it to remove iron from water taking into account the effects of applied current density (ACD), the pH of the water (PoW), iron concentration (IC) and treatment time (TT). The effects of these parameters were optimised using the Box-Behnken model. Synthetic water samples containing different concentrations of iron (10-30 mg/l), were treated in a continuous flow, using the new EC reactor at different ACD (1.5-4.5 mA/cm2), PoW (4-10) and TT (10-50 min). The results revealed that the removal of 99.9% of iron was achieved by keeping PoW, ACD, IC and TT at 7, 3 mA/cm2, 10 mg/l and 50 min, respectively. The effects of ACD, POW, IC and TT on iron removal could be successfully simulated with R2 = 0.9788. The cost of removing iron using the proposed EC unit was 0.623 £/m3.

Perioperative diaphragm point-of-care ultrasound as a prediction tool of postoperative respiratory failure in high-risk patients: A feasibility study and case series. / Ecografía diafragmática perioperatoria en el punto de atención como herramienta de predicción de fallo respiratorio postoperatorio en pacientes de alto riesgo: estudio de viabilidad y serie de casos.

INTRODUCTION: Respiratory muscle function in the postoperative period is a key to whether a patient develops Postoperative Respiratory Failure (PRF) or not. PRF occurs when the gas exchange does not meet metabolic needs. Ipsilateral paralysis of the hemidiaphragm after interscalenic brachial plexus block (ISB) causes an acute reduction of respiratory muscle function. This reduction does not cause PRF when the contralateral hemidiaphragm generates enough gas exchange to meet metabolic demands. OBJECTIVES: To study the evolution of hemidiaphragmatic muscle function during the perioperative period with diaphragmatic ultrasound (D-POCUS), and use it as an innovative tool to predict PRF, assessing the contralateral hemidiaphragm in the event of acute hemidiaphragm paralysis. METHODS: Patients considered high risk, scheduled for shoulder surgery with ISB are studied. Both hemidiaphragms were evaluated by ultrasound, before and after the procedure, measuring Thickening Fraction (TF) and Diaphragmatic Excursion (DE). PACU patients with PRF were registered. RESULTS: There was a significant reduction in the TF and DE of the ipsilateral hemidiaphragm in the six patients studied. Only 1/6 patients showed signs of PRF. The evaluation of the contralateral hemidiaphragm during the postoperative period showed that in the five patients without signs of PRF, there were no significant changes in the function of the contralateral hemidiaphragm. The patient, who showed a reduction in contralateral hemidiaphragm function, was the only one who suffered PRF. CONCLUSIONS: In this case series, D-POCUS allows to know the perioperative function of the diaphragm in high-risk patients. All patients suffered an acute reduction of hemidiaphragm function after ISB; however, these patients did not develop PRF when the contralateral hemidiaphragm function was preserved.

Removal of phosphate from River water using a new baffle plates electrochemical reactor.

During the last 50 years, the human activities have significantly altered the natural cycle of phosphate in this planet, causing phosphate to accumulate in the freshwater ecosystems of some countries to at least 75% greater than preindustrial levels, which indicates an urgent need to develop efficient phosphate treatment methods. Therefore, the current study investigates the removal of phosphate from river water using a new electrochemical cell (PBPR). This new cell utilises perforated baffle plates as a water mixer rather than magnetic stirrers that require power to work. This study investigates the influence of key operational parameters such as initial pH (ipH), current density (Ј), inter-electrode distance (ID), detention time (t) and initial phosphate concentration (IC) on the removal efficiency, and influence of the electrocoagulation process on the morphology of the surface of electrodes. Overall, the results showed that the new reactor was efficient enough to reduce the concentration of phosphate to the permissible limits. Additionally, SEM images showed that the Al anode became rough and nonuniform due to the production of aluminium hydroxides. The main advantages of the electrocoagulation technique are: •The EC method does not produce secondary pollutants as it does not required chemical additives, while other traditional treatment methods required either chemical or biological additives [[1], [2], [3], [4]].•It has a large treatment capacity and a relatively short treatment time in comparison with other treatment methods, such as the biological methods [1,[5], [6], [7]].•The EC method produces less sludge than traditional treatment traditional chemical and biological treatment methods [8,9]. EC technology, like any other treatment method, has some drawbacks that could limit its performance. For instance, it still has a clear deficiency in the variety of reactor design, and the electrodes should be periodically replaced as they dissolve into the solution due to the oxidation process [2,10].

Utilidad de la procalcitonina para el diagnóstico de infección en el paciente crítico con cirrosis hepática / Usefulness of procalcitonin for diagnosing infection in critically ill patients with liver cirrhosis

OBJETIVO: Analizar la utilidad de la procalcitonina (PCT) para el diagnóstico de infección en pacientes con cirrosis hepática ingresados en una unidad de cuidados intensivos. DISEÑO: Estudio observacional retrospectivo. ÁMBITO: unidad de cuidados intensivos. polivalente, 24 camas. PARTICIPANTES: Pacientes con cirrosis hepática ingresados en nuestra unidad de cuidados intensivos en los últimos 4 años con diagnóstico de sospecha de infección y determinación de PCT. RESULTADOS: Entre los 255 pacientes con cirrosis ingresados en nuestra unidad; se determinó la PCT para el diagnóstico diferencial de infección en 69 casos (27%). Tres pacientes fueron excluidos del análisis por falta de datos clínicos. La estancia media fue de 10,6 ± 9,2 días y la mortalidad del 65%. El origen de la cirrosis fue vírico (57%) o enólico (37%), con una puntuación de 9,5 ± 2 en la escala de Child-Pugh y 23±8 en la escala de MELD. En 54 pacientes (82%) se estableció el diagnóstico de infección. La infección más frecuente fue la neumonía (72%), seguida de la infección intraabdominal (18%), y la bacteriemia (5%). En los pacientes sin infección la mediana de PCT fue de 0,57 ng/ml (0,28-1,14) frente a 2,99 (1,31-9,4) p < 0,001 en aquellos con infección. La capacidad diagnóstica se mantuvo en los pacientes con infección intraabdominal. El punto de corte diagnóstico se estableció en 0,8ng/ml (sensibilidad 83%, especificidad 75%, AUC 0,82 [0,702-0,93]). CONCLUSIONES: En los pacientes con cirrosis hepática la PCT es útil para identificar la presencia de infecciones bacterianas incluyendo las intraabdominales

OBJECTIVE: To evaluate the usefulness of procalcitonin (PCT) for diagnosing infection in patients with liver cirrhosis admitted to an Intensive Care Unit. DESIGN: A retrospective study was carried out. SCOPE: Intensive Care Unit. Versatile, twenty-four beds. PARTICIPANTS: Patients with liver cirrhosis admitted to our Intensive Care Unit in the last four years with suspected infection and measurement of PCT. RESULTS: Among the 255 patients with cirrhosis admitted to our unit, PCT was determined for the differential diagnosis of infection in 69 cases (27%). Three patients were excluded from analysis due to a lack of clinical data. The average stay was 10.6 ± 9.2 days, with a mortality rate of 65%. The origin of cirrhosis was mainly viral (57%) or alcoholic (37%). The Child-Pugh and MELD scores were 9.5±2 and 23±8, respectively. Infection was diagnosed in 54 patients (82%). The most common infection was pneumonia (72%), followed by intraabdominal infections (18%) and bacteremia (5%). In patients without infection, the median PCT concentration was 0.57ng/ml (range 0.28 to 1.14) versus 2.99 (1.31 to 9.4) in those with infection (p <.001). Diagnostic capacity was maintained in patients with intraabdominal infections. The diagnostic cutoff point was set at 0.8ng/ml (sensitivity 83%, specificity 75%, AUC 0.82 [0.702-0.93]). CONCLUSIONS: In patients with liver cirrhosis, PCT is useful for identifying bacterial infections, including intraabdominal processes

[Usefulness of procalcitonin for diagnosing infection in critically ill patients with liver cirrhosis]. / Utilidad de la procalcitonina para el diagnóstico de infección en el paciente crítico con cirrosis hepatica.

OBJECTIVE: To evaluate the usefulness of procalcitonin (PCT) for diagnosing infection in patients with liver cirrhosis admitted to an Intensive Care Unit. DESIGN: A retrospective study was carried out. SCOPE: Intensive Care Unit. Versatile, twenty-four beds. Participants Patients with liver cirrhosis admitted to our Intensive Care Unit in the last four years with suspected infection and measurement of PCT. RESULTS: Among the 255 patients with cirrhosis admitted to our unit, PCT was determined for the differential diagnosis of infection in 69 cases (27%). Three patients were excluded from analysis due to a lack of clinical data. The average stay was 10.6 ± 9.2 days, with a mortality rate of 65%. The origin of cirrhosis was mainly viral (57%) or alcoholic (37%). The Child-Pugh and MELD scores were 9.5 ± 2 and 23 ± 8, respectively. Infection was diagnosed in 54 patients (82%). The most common infection was pneumonia (72%), followed by intraabdominal infections (18%) and bacteremia (5%). In patients without infection, the median PCT concentration was 0.57 ng/ml (range 0.28 to 1.14) versus 2.99 (1.31 to 9.4) in those with infection (p<.001). Diagnostic capacity was maintained in patients with intraabdominal infections. The diagnostic cutoff point was set at 0.8 ng/ml (sensitivity 83%, specificity 75%, AUC 0.82 [0.702-0.93]). CONCLUSIONS: In patients with liver cirrhosis, PCT is useful for identifying bacterial infections, including intraabdominal processes.

Intensive care practices in brain death diagnosis and organ donation.

We conducted a multicentre study of 1844 patients from 42 Spanish intensive care units, and analysed the clinical characteristics of brain death, the use of ancillary testing, and the clinical decisions taken after the diagnosis of brain death. The main cause of brain death was intracerebral haemorrhage (769/1844, 42%), followed by traumatic brain injury (343/1844, 19%) and subarachnoid haemorrhage (257/1844, 14%). The diagnosis of brain death was made rapidly (50% in the first 24 h). Of those patients who went on to die, the Glasgow Coma Scale on admission was ≤ 8/15 in 1146/1261 (91%) of patients with intracerebral haemorrhage, traumatic brain injury or anoxic encephalopathy; the Hunt and Hess Scale was 4-5 in 207/251 (83%) of patients following subarachnoid haemorrhage; and the National Institutes of Health Stroke Scale was ≥ 15 in 114/129 (89%) of patients with strokes. Brain death was diagnosed exclusively by clinical examination in 92/1844 (5%) of cases. Electroencephalography was the most frequently used ancillary test (1303/1752, 70.7%), followed by transcranial Doppler (652/1752, 37%). Organ donation took place in 70% of patients (1291/1844), with medical unsuitability (267/553, 48%) and family refusal (244/553, 13%) the main reasons for loss of potential donors. All life-sustaining measures were withdrawn in 413/553 of non-donors (75%).

Parada cardíaca por hipotermia accidental y resucitación cardiopulmonar prolongada / Cardiac arrest due to accidental hypothermia and prolonged cardiopulmonary resuscitation

En la parada cardíaca por hipotermia la reanimación cardiopulmonar debe prolongarse hasta que se recupere una temperatura corporal normal. Existen diversos métodos de recalentamiento. En teoría, los métodos más cruentos son los de elección en los casos de parada cardíaca porque con ellos se consigue un recalentamiento más veloz, pero su supuesta superioridad sobre otros métodos menos cruentos no está demostrada. Presentamos un caso de hipotermia accidental con parada cardíaca que se trató con masaje cardíaco ininterrumpidamente durante 3h, lo que constituye la reanimación cardiopulmonar con éxito más larga notificada hasta ahora en España. Para recalentar el cuerpo se utilizó una combinación de métodos poco cruentos: recalentamiento activo externo con una tobera de aire caliente, lavado gástrico y vesical con suero caliente e infusión de suero fisiológico caliente. Este caso demuestra que es posible tratar satisfactoriamente la parada cardíaca por hipotermia mediante estos métodos de recalentamiento, rápidos de instaurar y accesibles en cualquier hospital (AU)

In cardiac arrest produced by accidental hypothermia, cardiopulmonary resuscitation must be prolonged until normal body temperature is achieved. There are different rewarming methods. In theory, the more invasive ones are elective in patients with cardiac arrest because of their higher rewarming speed. However, it has not been proven that these methods are better than the non-invasive ones. We present a case report of a patient with cardiac arrest due to accidental hypothermia who was treated without interruption for three hours with heart massage. This is the longest successful cardiopulmonary resuscitation known up-to-date in Spain. In order to rewarm the body, a combination of non-invasive methods was used: active external rewarming with convective warm air, gastric and bladder lavage with warm saline solution and intravenous warm saline infusion. This case shows that it is possible to treat hypothermic cardiac arrest successfully through these rewarming methods, which are both easy to apply and feasible in any hospital (AU)

[Cardiac arrest due to accidental hypothermia and prolonged cardiopulmonary resuscitation]. / Parada cardíaca por hipotermia accidental y resucitación cardiopulmonar prolongada.

In cardiac arrest produced by accidental hypothermia, cardiopulmonary resuscitation must be prolonged until normal body temperature is achieved. There are different rewarming methods. In theory, the more invasive ones are elective in patients with cardiac arrest because of their higher rewarming speed. However, it has not been proven that these methods are better than the non-invasive ones. We present a case report of a patient with cardiac arrest due to accidental hypothermia who was treated without interruption for three hours with heart massage. This is the longest successful cardiopulmonary resuscitation known up-to-date in Spain. In order to rewarm the body, a combination of non-invasive methods was used: active external rewarming with convective warm air, gastric and bladder lavage with warm saline solution and intravenous warm saline infusion. This case shows that it is possible to treat hypothermic cardiac arrest successfully through these rewarming methods, which are both easy to apply and feasible in any hospital.

Relationship of hydraulic impedance and elasticity in the pulmonary artery of maturing newborn pigs.

The current study determined the dynamic stress-strain elastic moduli (E(Y)) and characteristic impedances (Z(0(2-7Hz))) of the main pulmonary artery in open-chest, anesthetized newborn pigs at 2 days, 2 weeks, and 3 months of age. E(Y) and Z(0(2-7Hz)) were compared to those values derived from the Womersley and Moens-Korteweg equations (denoted E(W-MK) and Z(0W-MK), respectively) to test the validity of these equations in describing the elasticity of the intact newborn pulmonary artery. E(Y) was defined as the ratio of stress to strain. The current study hypothesized that: (1) E(Y) and E(W-MK) are numerically similar, and therefore the Womersley and Moens-Korteweg equations accurately describe the viscoelastic properties of the main pulmonary artery of the newborn pig, and (2) that both E(Y) and Z(0) are elevated at birth and undergo a steady decline with maturation. E(Y) was not significantly different from E(W-MK), while Z(0(2-7Hz)) was nearly identical to Z(0W-MK) in all groups. The elastic modulus peaked (P < 0.001) in 2-week-old pigs compared with both younger and older animals, while Z(0(2-7Hz)) decreased with increasing age (48 h = 1237 +/- 251 [SEM] dyn s cm(-5), 2-week = 433 +/- 95 dyn s cm(-5), 3 month = 162 +/- 17 dyn s cm(-5), P < 0.001). These experiments validate the Womersley and Moens-Korteweg equations as accurately describing the elastic properties of the intact newborn pig pulmonary artery. These data also demonstrate that a diminution in Z(0) may occur even with increased wall stiffness, as observed in our 2-week-old pigs.

Characterization of the pulmonary arterial response to endothelin-1 and bosentan in neonatal pigs.

BACKGROUND: This study determined the pulmonary vascular responses to intravenous (IV) administration of endothelin-1 (ET-1) before and after an IV bolus of bosentan (Ro 47-0203), an endothelin receptor antagonist, in anesthetized open-chest 48-hour-old and 2-week-old Yorkshire pigs. METHODS: Eighteen 48-hour-old and 25 2-week-old pigs were randomly allocated to receive either (1) 400 ng x kg(-1) x min(-1) of ET-1 or (2) 5 mg/kg or 10 mg/kg of Ro 47-0203 followed by 400 ng x kg(-1) x min(-1) of ET-1 over a 10-minute interval. Pulmonary vascular resistance (PVR, dyne sec/cm(-5)), elastic modulus (E(Yo), dyne/cm2), and characteristic impedance (Zo) were determined (+/- SEM). RESULTS: In 48-hour-old pigs, ET-1 decreased pulmonary artery pressure (PAP, dyne/cm2; 21,317 +/- 1,833 versus 17,757 +/- 1,823; p = 0.003). In 2-week-old pigs, ET-1 elevated PAP (19,009 +/- 1,834 versus 21,935 +/- 2,104; p = 0.003) and PVR (1,624 +/- 254 versus 2,302 +/- 416; p = 0.001), whereas bosentan abolished the ET-1 induced pulmonary and systemic vasoconstriction. Neither agent altered E(Y) or Z(o). CONCLUSIONS: ET-1 caused a pulmonary depressor response in 48-hour-old pigs and a constrictor response in 2-week-old pigs, whereas bosentan inhibited the ET-1 induced pulmonary arteriolar vasoconstriction in 2-week-old pigs. The response to ET-1 changes from dilation in 48-hour-old pigs (neonates) to constriction in 2-week-old pigs (infants) suggests a maturational dependent alteration in ET receptors during the first 2 weeks of life. These data suggest that bosentan may have potential clinical application in the treatment of newborn pulmonary hypertensive episodes as it ablated ET-1 induced pulmonary vasoconstriction, while maintaining systemic pressure.

Closure of the ductus arteriosus--new insights for critical care.

New insights into the closure of the ductus arteriosus may lead to more effective nonsurgical treatment in patent ductus arteriosus. ET-1 agonists may prove useful in future pharmacologic interventions.

Endothelin-1: possible implications in pulmonary vascular disease.

The vasoactive properties of endothelin-1 (ET-1) in the animal model very with the tone of the pulmonary vessels, the dose level of ET-1, and the maturation of the vessels. The action of ET-1 is mediated by endothelium-derived nitric oxide, prostaglandins, and electrolytes. Plasma levels of ET-1 are elevated in pulmonary hypertension in both animals and humans. ET-1 antagonists may prove useful in treating pulmonary hypertension in children and adults.

High-altitude pulmonary edema: a clinical crisis.

High-altitude pulmonary edema is a serious clinical condition observed in individuals participating in mountain climbing and skiing at high altitudes. High-altitude pulmonary edema is an oncardiogenic form of pulmonary edema. Atrial natriuretic factor and endothelin are implicated and ventilatory support is important in preventing fatalities.

The role of N omega-nitro-L-arginine in modulation of pulmonary vascular tone in the maturing newborn pig.

Current therapeutic modalities for treatment of newborn pulmonary hypertensive crisis include but are not limited to the administration of nitric oxide (endothelium-derived relaxing factor). However, few data are available on the role of endogenously produced endothelium-derived relaxing factor in the modulation of pulmonary vascular tone in the neonate. In the current study, we investigated the acute effects of N omega-nitro-L-arginine (a potent competitive inhibitor of endothelium-derived relaxing factor synthase) on the pulmonary vasculature of anesthesized open-chest 48-hour-old (n = 8) and 2-week-old (n = 7) Yorkshire pigs. After baseline data were acquired, all animals received a 10 mg/kg per minute infusion of N omega-nitro-L-arginine for 10 minutes. To discern distal and proximal pulmonary arterial vessel changes, input mean and characteristic impedance were respectively determined. Pulmonary vascular resistance was also calculated (units determined in dyne.sec.cm-5 plus or minus the standard error of the mean). Results showed N omega-nitro-L-arginine infusion did not significantly alter baseline pulmonary arterial pressure (22,370 +/- 1473 dyne/cm2), pulmonary vascular resistance (5171 +/- 805 dyne.sec.cm-5), input impedance (6343 +/- 806 dyne.sec.cm-5), or characteristic impedance (2073 +/- 418 dyne.sec.cm-5) in 48-hour-old pigs. In 2-week-old pigs, infusion of N omega-nitro-L-arginine elevated pulmonary arterial pressure (18,162 +/- 1415 dyne/cm2 versus 23,838 +/- 1810 dyne/cm2, p = 0.015), pulmonary vascular resistance (810 +/- 137 dyne.sec.cm-5 versus 1519 dyne.sec.cm-5, p = 0.030), and input impedance (2302 +/- 251 dyne.sec.cm-5 versus 2900 +/- 255 dyne.sec.cm-5, p = 0.018). Characteristic impedance was not altered in 2-week-old pigs. These data indicate that N omega-nitro-L-arginine infusion resulted in pulmonary arteriolar vasoconstriction in 2-week-old pigs, but not in 48-hour-old pigs. This finding suggests that endothelium-derived relaxing factor does not modulate basal pulmonary arteriolar tone during the early newborn period, but does play a significant role in 2-week-old pigs. These data also suggest that the functional role for endothelium-derived relaxing factor is confined to the distal arteriolar pulmonary bed and does not extend to the larger proximal arterial vessels.

Pathophysiology of pulmonary edema.

Pulmonary edema is a frequent and common cause of death in patients in critical care settings. It is seen as a complication of myocardial infarcts, hypertension, pneumonia, smoke inhalation, and high-altitude pulmonary edema. Pulmonary edema occurs when there are alterations in Starling forces and capillary permeability, opposition to lymphatic flow in the lungs, decreased plasma oncotic pressure, central nervous system lesions, and following some types of strenuous exercise. Pulmonary edema presents initially with crackles, wheezing, and dry cough and progresses to tachypnea, dyspnea, orthopnea, pink frothy sputum, and cyanosis. Treatment involves supportive therapy, reduction in blood volume, and oxygen therapy.

Pulmonary hydraulic impedance responses to hypoxia and hypercapnia in newborn pigs.

The purpose of this study was to determine the cumulative effects of brief intervals of hypoxia and hypercapnia on the pulsatile characteristics of the pulmonary arterial circulation of 48-h-old compared with 2-wk-old open-chest Yorkshire pigs while using two different anesthetic regimens: 1) azaperone and ketamine (4 and 12 mg/kg im, respectively) and 2) thiopental sodium (25 mg/kg i.v.). Animals 48 h old were randomly allocated to undergo mild hypoxia (inspired O2 fraction = 0.15), severe hypoxia (inspired O2 fraction = 0.05), or hypercapnia (inspired CO2 fraction = 0.20), whereas animals 2 wk old underwent severe hypoxia or hypercapnia. With use of Fourier analysis, characteristic impedance (Zo), mean input impedance (Zm), impedance moduli, and phase angles were determined. In 48-h-old pigs anesthetized with azaperone-ketamine, neither mild nor severe hypoxia altered Zo, Zm, or pulmonary vascular resistance (PVR), whereas hypercapnia increased Zo by 22% (P < 0.001), which persisted despite a return to normocapnia. In 48-h-old animals anesthetized with thiopental, baseline control Zo and Zm were lower than those in same-age pigs anesthetized with azaperone-ketamine. In thiopental-anesthetized 48-h-old pigs, both severe hypoxia and hypercapnia increased Zm and PVR but Zo was unaltered. In 2-wk-old pigs anesthetized with thiopental, severe hypoxia but not hypercapnia elevated Zm and PVR, whereas Zo was not changed with either stress. Results indicate age- and anesthetic-dependent responses of Zo, Zm, and PVR to severe hypoxia and hypercapnia. The persistent elevation in Zo caused by hypercapnia indicates a prolonged decrease in arterial compliance or a reduction in effective proximal pulmonary arterial radius.

Pulmonary hydraulic impedance response to cromakalim (BRL 34915) in newborn pigs.

Cromakalim (BRL 34915), a novel vasodilator, is used clinically to manage systemic hypertension. Its effects on the intact newborn pulmonary circulation remain unclear. The purpose of this study was to determine the response of both the mean and pulsatile pulmonary hemodynamic parameters to intravenous infusion of BRL 34915 (0.1 mg/kg/min for 10 min) in 48-hr-old open-chest Yorkshire pigs. Animals were divided into two groups: Group I pigs had a high mean baseline pulmonary artery pressure (PAP) (> 17 mm Hg), while Group II pigs had a low to normal baseline mean PAP (< 17 mm Hg). Following instrumentation for high-fidelity recordings of PAP and flow, baseline data were acquired. Employing Fourier analysis, characteristic impedance (Zo), input mean impedance (Zm), impedance harmonic moduli (units in dyn sec cm-5), and phase angles (radians) were determined. Pulmonary vascular resistance (PVR) was calculated and aortic pressure (AP, mm Hg) was also measured. All values = mean +/- SEM. Group I animals ("high tone") underwent a decrease in PAP (17.9 +/- 1.6 mm Hg vs 13.6 +/- 1.9 mm Hg, P = 0.008) and PVR (4310 +/- 816 dyn sec cm-5 vs 3713 +/- 687 dyn sec cm-5, P = 0.04). Group II animals ("low tone") responded with an increase in PAP (11.5 +/- 0.4 mm Hg vs 16.6 +/- 1.8 mm Hg, P = 0.029). AP decreased in Group I (40 +/- 3.8 mm Hg vs 21.5 +/- 2.8 mm Hg, P = 0.008) and Group II (51.2 +/- 10.8 mm Hg vs 31.2 +/- 10.9 mm Hg, P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Vasodilator effects of hydroxylamine in the isolated rodent lung.

Hydroxylamine is a natural product of cellular metabolism that possesses vasodilating properties similar to those of endothelium-derived relaxing factor (EDRF). In the rodent pulmonary circulation preconstricted with the endoperoxide analog U-46619, hydroxylamine relaxed the vasculature in a concentration-dependent manner. Blockade of the hydroxylamine vasodilator response by methylene blue indicated that the mechanism of vasorelaxation is similar to that of EDRF. In this preparation, hydroxylamine is a more potent vasodilator than nitroglycerin.

Calcium utilization associated with U-46619 and PGF2a vascular responses in rat lungs.

The pulmonary vasoconstrictor responses to U-46619 and PGF2a are calcium dependent. The purpose of this investigation was to determine to what extent extracellular and intracellular calcium pools are utilized during the dose-dependent pulmonary vasopressor responses induced by multiple doses of U-46619 and PGF2a. Increasing doses of these agonists were administered to isolated rat lungs perfused with Krebs-Ringer bicarbonate (KRB) or KRB not containing CaCL2. The data indicate that U-46619 uses predominantly extracellular calcium at low doses (0.1 microgram) and depends solely on intracellular calcium at the highest dose (0.4 microgram). In contrast PGF2a appears to use depletable intracellular calcium stores to achieve contraction.